GRACANICA, Serbia-Montenegro — NATO-led peacekeepers in Kosovo smashed through doors and tossed stun grenades in predawn raids Tuesday to collect evidence on what caused the worst ethnic violence here since the 1999 war.

About 200 peacekeepers raided four houses in Obilic, a city just outside the provincial capital, Pristina. Norwegian forces arrested two people and stuffed evidence in trash bags, seeking clues on who was behind the clashes between Serbs and ethnic Albanians that killed 28, destroyed 366 homes and burned 41 churches. In all, 196 people have been arrested.

Two police officers were shot to death in a morning attack in the village of Sakovica, some 15 miles north of the capital, said U.N. police spokesman Derek Chappell.

The police vehicle was riddled with bullets. NATO-led peacekeepers arrived at the scene and started searching a small hill nearby with flashlights.

“This is a very extensive crime scene,” Chappell said. “A lot of bullets have been fired.”

'Crimes against humanity'The top U.N. official in Kosovo declared that there was organization behind the violence. Harri Holkeri said those behind the attacks “tried to destroy the whole future of Kosovo.”

“They are responsible for severe crimes against humanity,” Holkeri said.

The NATO commander in the central part of Kosovo apologized for failing to anticipate the potential for violence in a province where tensions still simmer five years after the end of the war.

“We got it wrong,” Swedish Brig. Gen. Anders Braennstroem said at a meeting with leaders from the Serb communities near Pristina. “For that I am very sorry.”

Last week’s attacks were the worst outbreak of violence since 1999, when a NATO air war ended a Serb crackdown on ethnic Albanians seeking independence. The war killed 10,000 ethnic Albanians.

Kosovo has been an international protectorate since then, its final status to be decided by the United Nations. For now, it officially remains a part of Serbia-Montenegro, the successor state of Yugoslavia.

Days of riot
The deaths of two boys in an incident blamed on the Serbs triggered days of rioting, looting and arson by ethnic Albanians. About 600 people were injured and 4,000 were homeless by week’s end.

About 180 Serbs left homeless by the violence tried to leave the province or travel to the province’s largest Serb enclave with little success Tuesday. Peacekeepers escorted the Serbs off a NATO base where they had taken shelter, but local leaders backed down on promises to provide buses or other transportation for them to leave.

Weeping women stood in front of buses that had taken them from the NATO base to the Serb enclave of Gracanica, insisting they had been promised passage to places they felt safer under an agreement with local Serb officials. The deal had been witnessed by an officer serving with NATO-led peacekeepers.

“They promised! They promised!” said Milica Todorovic, 48, who became hysterical after learning she would have to stay on a cot in a school converted to an emergency shelter. “We don’t want to come here.”

To leave or to stayThe incident underlined the tremendous pressure being placed on the remaining 100,000 or so Orthodox Christian Serbs in Kosovo. Many wish to leave, fearing further attacks in the mostly Muslim ethnic Albanian-dominated province. But Serb leaders want them to stay so they can retain their territorial claims on the province, which is run by the United Nations but remains part of Serbia-Montenegro.

Meanwhile, several thousand ethnic Albanians walked toward the cemetery in the divided city of Kosovska Mitrovica to attend the funerals of four men who were killed in last week’s riots. Local leaders appealed for calm.

Two NATO helicopters hovered overhead while mourners held a minute of silence. They buried the men in coffins draped with Albanian flags, and said they died while demonstrating to unite the city.

“We feel great pain and pride,” said Halil Haliti, the uncle of one of the dead. “His death has strengthened our determination not to let the city go and achieve independence.”